The invention relates to a hydrostatic drive comprising a dual-acting hydraulic cylinder and volumetric flow equalisation.
It is known from DE 103 43 016 A1 to actuate a dual-acting hydraulic cylinder by means of a first hydraulic pump and a second hydraulic pump. One of the two hydraulic pumps is, in this case, connected to the two working chambers of the dual-acting hydraulic cylinder in a closed circuit. The second hydraulic pump is, however, only connected to the working chamber on the piston side, in an open circuit. The two hydraulic pumps are respectively able to be adjusted in their delivery volume. By setting a corresponding delivery volume ratio, the different volumetric flows in the working chamber on the piston side and the working chamber on the piston rod side are taken into account.
A drawback with the hydrostatic drive known from DE 103 43 016 A1 is that the ratio between the sum of the delivery volumes of the two hydraulic pumps and the delivery volume of the hydraulic pump in the closed circuit respectively has to remain at the same ratio as the piston surfaces of the working piston relative to one another. If, as a result, two identical hydraulic pumps are used, the respective delivery volume thereof has to be set by the appropriate adjusting devices, so that said condition is fulfilled. In contrast, it is necessary when using two identical hydraulic pumps, as may be implemented advantageously by using a double pump, to use a dual-acting hydraulic cylinder, the piston surfaces thereof having an appropriate ratio. Generally, the two hydraulic pumps of a double pump unit are configured to be identical, so that the area ratio of the two piston surfaces would have to be 2:1. Conventional dual-acting hydraulic cylinders, however, generally have an area ratio of the piston surfaces which differs therefrom and thus different volumetric flows when displacing the working piston.